1. Field of the Invention
The invention relates to a common rail for a common rail fuel injection system of an internal combustion engine, having a tubular base body which is equipped with a plurality of connection openings.
2. Description of the Prior Art
In common rail injection systems, a high-pressure pump, optionally with the aid of a prefeed pump, pumps the fuel to be injected from a tank into the central high-pressure fuel reservoir, which is called a common rail. From the rail, fuel lines lead to the individual injectors, which are assigned to the engine cylinders. The injectors are triggered individually by the engine electronics as a function of the engine operating parameters, in order to inject fuel into the combustion chamber of the engine. The pressure generation and the injection are decoupled from one another by the common rail.
A conventional common rail is described for instance in German Patent Disclosure DE 195 48 611. The conventional common rails withstand pressures of up to about 1100 bar.
The primary object of the invention is to furnish a common rail of the type described above that withstands higher pressures than conventional common rails. In addition, the common rail according to the invention should be simple in construction, and it should be possible to produce it economically.
In a common rail for a common rail fuel injection system of an internal combustion engine, having a tubular base body which is equipped with a plurality of connection openings, this object is attained in that at least two connection openings, or a connecting opening and a machining opening, are disposed diametrically opposite one another in the tubular base body. With the context of the present invention, it has been found that the high-pressure strength of the common rail is limited primarily by the intersections between the connection openings and the tubular base body. The diametrically opposed connection openings provide easy access for a machining tool. This simplifies machining the interfaces between the connection openings and tubular base body considerably. The transitions between the connection openings and the tubular base body can be rounded much more simply than in conventional common rails. The common rail of the invention withstands pressures of over 2000 bar. The best results are obtained if all the connection openings are disposed in pairs of diametrically opposed openings.
In a common rail for a common rail fuel injection system of an internal combustion engine, having a tubular base body which is equipped with a plurality of connection openings, the above-stated object is also attained in that diametrically opposite at least one of the connection openings, there is a machining opening, which is closed by a closure plug. The additional machining openings offer the advantage that the location of the connection openings can be selected freely. Through the machining opening diametrically opposite the connection opening, the critical interface between the connection opening and the tubular base body is reached more easily with a machining tool. After the machining of the connection opening, the diametrically opposed machining opening is closed with the closure plug. The machining of the transition between the machining opening and the tubular base body is logically done through the opposed connection opening. Examples of machining methods are rounding and smoothing using profiling cutters or grinders, by introducing intrinsic pressure stresses into the critical regions with the aid of a fitting that is pressed into the critical regions, by hydrogrinding processes, or by electrochemical erosion. The requisite machining of the machining opening for high-pressure strength can also be effected by the machining opening itself. The best results are obtained if one machining opening is disposed diametrically opposite each of the connection openings, or a further connection opening is disposed diametrically opposite each of the connection openings.
In one embodiment of the invention, the closure plug is formed of a memory material, in particular a metal memory material.
In another embodiment of the invention the closure plug is equipped with a thread that cooperates with a complimentary thread on the machining opening. It is understood that it is also possible to secure the closure plug in the associated machining opening in a manner proof against high pressure with the aid of a welded connection.
A further embodiment of the invention is characterized in that means for securing the common rail to the engine are provided on the closure plug. This simplifies the construction and production of the common rail considerably.
A further embodiment of the invention is characterized in that the machining openings have a larger diameter than the connection openings. This improves the accessibility for a machining tool. The applies both to machining the connection openings and to machining the machining bores themselves.